DEPOSITS AND CUSTOMER REPURCHASE AGREEMENTS (Geographic Concentration of Deposits) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012
Deposit Liabilities [Line Items]
Total deposits	$ 3,520,584	$ 3,557,804	$ 3,426,170
Washington [Member]
Deposit Liabilities [Line Items]
Total deposits	2,665,776
Oregon [Member]
Deposit Liabilities [Line Items]
Total deposits	618,161
Idaho [Member]
Deposit Liabilities [Line Items]
Total deposits	$ 236,647